Beamforming training using echoes of an omnidirectional pulse

ABSTRACT

Methods and devices for estimating an angle between a transmitter and a receiver for beamforming are provided. A method includes, with an antenna element in a first device, transmitting an omnidirectional pulse and detecting an echo of the pulse reflected from a second device. An angle between the first device and the second device is estimated based at least on a characteristic of the echo. The method includes transmitting the angle to the second device for use in beamforming between the first device and the second device.

FIELD

The present disclosure relates to the field of radio frequency (RF)transceiver antenna arrays and in particular to methods and apparatusfor beamforming between directional wireless links.

BACKGROUND

Data throughput of multi-Gbps over wireless communication links togetherwith substantially improved spectrum and energy efficiency have led toutilization of the radio spectrum above 6 GHz for indoor and outdoorapplications in 5G cellular mobile systems, local multipointdistribution services, cellular backhaul and intra-cell communicationsystems. Due to the high path and penetration losses, in particular atfrequency bands with millimeter wavelengths, antenna beamforming playsan important role in establishing and maintaining a robust communicationlink. To perform beamforming, the communicating transmitter, receiver,and transceiver determine and continuously maintain an optimal alignedpair of receive and transmit antenna sectors that optimize signalquality and throughput. Each determination of the optimal aligned pairof receive and transmit antenna sectors involves a process that can takeseveral milliseconds.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an exemplary two-way beamforming training process tosetup and refine an optimal aligned pair of receive and transmit antennasectors for wireless communication links.

FIG. 1B illustrates an exemplary two-way transmit and receive sectorsweep process for wireless communication links.

FIG. 2 illustrates schematically an exemplary modular antenna array withantenna elements.

FIG. 3 illustrates one exemplary transmitter and receiver angleestimation process, in accordance with various aspects described.

FIG. 4 illustrates an exemplary beamforming training process todetermine an optimal aligned pair of receive and transmit antennasectors for wireless communication links, in accordance with variousaspects described.

FIG. 5 illustrates another exemplary beamforming training process torefine the optimal aligned pair of receive and transmit antenna sectorsfor wireless communication links, in accordance with various aspectsdescribed.

FIG. 6 illustrates an exemplary beamforming training process todetermine an optimal aligned pair of receive and transmit antennasectors for multiple wireless communication links, in accordance withvarious aspects described.

FIG. 7 illustrates a flow diagram outlining an exemplary method forbeamforming training to determine an optimal aligned pair of receive andtransmit antenna sectors, in accordance with various aspects described.

FIG. 8 illustrates an example user equipment device that is configuredto perform angle estimation in accordance with various aspectsdescribed.

DETAILED DESCRIPTION

The present disclosure will now be described with reference to theattached drawing figures, wherein like reference numerals are used torefer to like elements throughout, and wherein the illustratedstructures and devices are not necessarily drawn to scale. As utilizedherein, terms “component,” “system,” “interface,” “circuitry” and thelike are intended to refer to a computer-related entity, hardware,software (e.g., in execution), and/or firmware. For example, a circuitrycan be a circuit, a processor, a process running on a processor, acontroller, an object, an executable, a program, a storage device,and/or a computer with a processing device.

FIG. 1A illustrates a beamforming training process 100 used to determinethe optimal transmit and receive antenna sectors for wirelesscommunication links as specified by IEEE 802.11ad. The beamformingtraining process includes two phases, a sector-level sweep (SLS) phaseand a beam refinement phase (BRP). In the SLS phase the transmitter (TXSTA) starts with an initial coarse-grain antenna sector sweep followedby a receiver (RX STA) initial coarse-grain antenna sector sweep inwhich the transmit antenna array and receive antenna array usepre-defined antenna beamforming patterns and avoid omnidirectionaltransmission by either the TX STA or the RX STA. The sweep leads to afirst coarse-grain antenna sector configuration with a common TX and RXantenna pair. In the beam refinement phase this first identified sectorpair is optionally used to fine-tune the TX and RX antenna arrays toselect a beam pattern pair with finer beam widths. There may also be anoptional beam tracking (BT) phase in which the beam is adjusted forchannel dynamics during data transmission. In the BT phase trainingfields including the automatic gain control (AGC) are added to datapackets. Within the AGC field the set of beam directions being trainedare changed in a sequential manner for the RX antenna array to calculatean appropriate AGC gain.

For the purposes of this description, the TX STA starts the beamformingtraining as the initiator and a mobile communication device (RX STA) isthe responder. Of course, the role of initiator and responder may beswitched. During the SLS phase, the TX STA sends training packets with apre-defined antenna bandwidth and the RX STA remains in aquasi-omnidirectional mode. The RX STA measures the signal strengthacross all sectors and replies with the sector ID with a maximumreceived signal strength as sector sweep feedback (SS-FB). The SLS phaseis illustrated schematically in FIG. 1B, in which eight differenttransmissions in eight different sectors are performed sequentially bythe TX STA and the RX STA responds by identifying the one out of foursectors (e.g., sector #2) having the strongest receive signal.

The sector-level sweep phase incudes an initiator sector sweep (ISS), aresponder sector sweep (RSS), sector sweep feedback (SS-FB), and sectorsweep acknowledgment (SS-ACK) as in FIG. 1A. The ISS, RSS, and SS-FB areenclosed in a dashed box in FIG. 1A to indicate that those functions arereplaced by the echo-based angle estimation that will be describedherein. During the beam refinement phase (BRP) the TX STA and the RX STAiteratively refine the beams found during the sector-level sweep phase.High resolution beam pairs inside and around the best sector, which areidentified during the SS phase, are tested and one beam pair is finallyselected during the BRP.

After accomplishment of the SLS and BRP phases, the best refined beampair is used for data transmission. Training sequences are appendedadditionally to payload data packets for channel estimation to adjustthe channel variations after SLS phase and BRP in order to achieve beamtracking. The SLS phase and BRP are typically executed at the startingof the beamforming process. The data transfer interval (DTI) can be usedfor beamforming phases to enable reappearance of the beamforming ondemand.

Beamforming for millimeter wave communications poses many challenges dueto the large channel bandwidth, very dynamic channel characteristics,and hardware constraints. In particular, beamforming training andtracking accounting for TX STA and RX STA mobility rely on resourceefficient schemes to accomplish line-of-sight (LOS) beam alignment andtracking under non-line-of-sight (NLOS) conditions. Therefore thebeamforming training for directional wireless links should be done veryquickly in particular when the mobile STA is moving directionally. Thusit would be advantageous to minimize the number of antenna sectors andthe number of refined beams to be tested during the SLS and BRP in orderto reduce beam training delay.

Current beam trainings take relatively long, ranging from single digitmilliseconds up to hundreds of milliseconds. The latency (sum of timetaken for SLS and BRP) is related to the number N of sectors served, thenumber M of beams per sector and the implemented search algorithm. Theantenna beam width and the antenna gains are further constraints, wherethe antenna gain is limited during the beam training due to the tradeoffbetween time and beam resolution. Finally, beamforming training consumessubstantial energy and processing resources, which are significantissues in devices operating at frequencies in millimeter wave bandswhere energy efficiency and latency are important issues.

The echo-based beamforming training described herein includes anecho-based angle estimation process for transmitters and receivers. Inecho-based angle estimation, echoes of omnidirectional pulsestransmitted by the TX STA (i.e., the initiator) are used to estimate theangle between the TX STA and the RX STA(s) (i.e., the responders). Thusecho-based angle estimation is performed in a manner in which the RX STAremains passive and does not transmit a responsive signal to the TX STA.The TX STA transmits omnidirectionally a pulse from one or more antennaelements and determines the angle between the TX STA and the RX STAbased on an echo of the omnidirectional pulse that is reflected backfrom the RX STA. This use of a reflected pulse (hereinafter “echo”)rather than a series of responsive communications from the RX STAsignificantly decreases the time for beamforming training and improvesenergy efficiency.

FIG. 2 illustrates, schematically, one embodiment of a modular antennaarray 200 that is present in the transmitter station TX STA (e.g., acellular communication tower, access point, and so on) and also in thereceiver station RX STA (e.g. a mobile communication device such as asmartphone or laptop). The antenna array 200 shown in FIG. 2 ispopulated with 8 antenna elements 210 to be used for beamforming, two“dummy” or reserved antenna elements 215, and two isotropic oromnidirectional antenna elements 220 a, 220 b. Of course, any number ofantenna elements 210, dummy antenna elements 215, omnidirectionalantenna elements 220, or other types of antenna elements may be presentin the modular antenna array, in other embodiments.

The antenna elements 210 are used to generate a directional antennaradiation patter used for directive transmit and receive, (i.e.,beamforming). The directional antenna elements 210 are optimized totransmit and receive a focused, directed signal or beam. The dummyantenna elements 215 are optional antenna elements that may be providedfor further sub-array extensions or other purposes. The omnidirectionalantenna elements 220 are used to broadcast signals in all directions andto receive broadcast signals from all directions. Thus, theomnidirectional antenna elements 220 a, 220 b are optimized to transmitand receive undirected signals. As such, the omnidirectional antennaelements are better suited for transmitting omnidirectional pulses thanare the directional antenna elements 210. The omnidirectional antennaelements 220 are often installed at the outer edges of the antenna arrayso they are relatively widely separated. The omnidirectional antennaelements 220 a, 220 b are spaced apart by a known distance D1. Theomnidirectional antenna elements 220 a, 220 b and their relatively widespacing are leveraged to perform echo-based beamforming training as willnow be described.

FIG. 3 illustrates one embodiment of an echo-based angle estimationprocess 300 that is part of echo-based beamforming training process andreplaces several time intensive operations in the SLS phase oftraditional beamforming training (see dashed box in FIG. 1A). For thepurposes of this description, the TX STA will be using echo-based angleestimation to determine or estimate the angle between the TX STA and theRX STA. However, in other embodiments, the RX STA may employ the sameecho-based beamforming training techniques to determine an angle betweenthe RX STA and the TX STA. In one embodiment, to estimate the angle βbetween the TX STA and the RX STA, angle estimator circuitry 330, whichis communicatively coupled to the antenna array 200, causes the twoomnidirectional antenna elements 220 a, 220 b to transmit aomnidirectional pulse. The pulse is considered to be bi-static becausetwo antenna elements simultaneously transmit the pulse. In otherembodiments, only a single omnidirectional antenna element transmits atimely separated sequence of omnidirectional pulses when it can beassumed that the transmitter is moving sufficiently between the pulses.

For the purposes of this description, a pulse is a signal that hasproperties that enhance detection of reflections of the pulse by thetransmitter of the pulse. Thus, a pulse can be distinguished from acommunication signal that encodes some underlying data to be decoded bythe receiver of the signal. Omnidirectional means that the signal isbroadcasted in a wide range of directions, possibly all directions. Anomnidirectional pulse may be optimized to travel a greater distance(e.g., have higher signal power) in all or most directions as comparedto a directed signal having a known receiver.

Examples of omnidirectional pulses may include a variety of codedpulses. The omnidirectional pulse transmitted by the antenna elements220 a, 220 b may be coded and compressed to overcome RX STA radar crosssection and link budget issues. A coded pulse may encode some knowninformation to enhance detection of the echo as amongst noise in asignal. Discrete coded waveforms may be used for the omnidirectionalpulse because these waveforms improve range characteristics anddetectability of the reflected pulse. For example, the pulse waveformmay be coded either with unmodulated pulse-train codes (uniform andstaggered) or phase modulated (binary or polyphaser) codes or frequencymodulated codes.

The omnidirectional antenna elements 220 a, 220 b are configured todetect or receive an echo, or reflection, of the pulse from the RX STAas shown by the two arrows in FIG. 3. The angle estimator circuitry 330is configured to distinguish an echo from an RX STA from echoesreflected from other sources such as buildings or hills. In oneembodiment, the angle estimator circuitry 330 analyzes received echoeswith matched filters to determine if the echo is from a communicationdevice of some sort (e.g., RX STA). The echo is to be distinguished froma communication signal that is actively transmitted by the RX STA to theTX STA. The angle estimator circuitry 330 may use additional echocharacteristics like Doppler to distinguish a RX STA from walls andother static objects. Furthermore, acknowledgement between the TX STAand the RX STA may be used to confirm that the echo was caused by the RXSTA.

The echo is a reflection of the pulse and does not result from anyresponsive communication from the RX STA. The RX STA is completelypassive because the echo is a reflection of the pulse from the RX STAand not a signal transmitted by the RX STA. Some characteristic of theecho is used by the angle estimator circuitry 330 to estimate the angleβ. For example, in one embodiment the respective times it takes for theecho to reach the respective antenna elements is used to estimate thedistance D2 between the first antenna element 220 a and the RX STA aswell as the distance D3 between the second antenna element 220 a and theRX STA. The angle estimator circuitry 330 thus can solve for the angle βbased on the three known sides D1, D2, D3 of a triangle.

FIG. 4 illustrates a portion of one embodiment of a beamforming trainingprocess that includes the echo-based angle estimation process 300. Afterestimating the angle based on the echo of the omnidirectional pulse, theTX STA transmits an angle identifier (A-ID) for the determined value ofβ to the RX STA. The RX STA sends an acknowledgement (SS-ACK) to the TXSTA to confirm its receipt of the A-ID. At this point, after determiningthe angle in a single iteration and without doing sector sweeps andsector sweep feedback as illustrated in FIG. 1A, the TX STA and RX STAfinalize the beamforming setup and refinement phase. While thebeamforming training sequence outlined in FIG. 1A is in accordance withthe IEEE 802.11ad framework, echo-based beamforming training outlined inFIG. 4 may be applied to any directional wireless technology that usesbeamforming training and tracking.

FIG. 5 illustrates one embodiment of echo-based beamforming training 500in which the RX STA also performs echo-based angle estimation 300 bytransmitting a pulse, detecting an echo reflected by the TX STA, andestimating the angle based on the echo. The RX STA transmits an A-ID forthe angle between the RX STA and the TX STA to the TX STA. Theecho-based beamforming training process 500 may be performed when the RXSTA fails to acknowledge receipt of the A-ID from the TX STA or when ahigher resolution angle value is desired. As shown in FIG. 6, in thisembodiment the RX STA is also equipped with an angle estimator circuitry630Rx that performs the same functions as the angle estimator circuitry330 of FIGS. 3 and 630Tx, possibly in response to a signal from theangle estimator circuitry 630Tx.

FIG. 6 illustrates one embodiment of an echo-based beamforming trainingprocess 600 in which the angle estimator circuitry 630Tx estimates theangle between the TX STA and four different RX STAs. Of course, anglesmay be estimated for as many RX STAs as are detectable to the TX STA. AtA, the angle estimator circuitry 630Tx causes omnidirectional antennaelements (not shown, see FIG. 2) to transmit an omnidirectional pulse.At B the antenna element detects an echo of the pulse that reflected offRX STA #4. Angle estimator circuitry 630Tx estimates an angle betweenthe TX STA and the RX STA #4 and transmits an A-ID to RX STA #4 so thatthe beam setup and refinement phase may begin. At C the antenna elementdetects the echo of the pulse that reflected off RX STA #3. Angleestimator circuitry 630Tx estimates an angle between the TX STA and theRX STA #3 and transmits an A-ID to RX STA #3 so that the beam setup andrefinement phase may begin. This process continues with echoes beingreceived in ascending order of distance. Thus, a single omnidirectionalpulse may be used to estimate the angle between the TX STA and anynumber of RX STAs.

FIG. 7 illustrates a flow diagram 700 that outlines one embodiment of amethod configured to perform echo-based beamforming training. The method700 may be performed by a first device that includes the angle estimatorcircuitry 330 of FIG. 3 and/or 630Tx, 630Rx of FIG. 6. The methodincludes, at 710, transmitting an omnidirectional pulse. At 720, an echoof the pulse reflected from a second device is detected. At 730, anangle between the first device and the second device is estimated basedon the echo. At 740, the angle (e.g., A-ID) is transmitted to the firstreceiver for use in beamforming setup and refinement with the firstreceiver. Optionally, at 750, acknowledgement of the angle is receivedfrom the first receiver and in response to receiving theacknowledgement, at 760 the beam setup and refinement phase is enteredwith the first receiver. At 770, a determination is made as to whetheror not another echo has been detected from a third device. If not, themethod ends. If so, the method returns to 730 and an angle between thethird device and the first device is estimated. In one embodiment, angleestimator circuitry comprises computer-executable instructions stored ona computer readable medium that, when executed by a computer associatedwith a TX STA, cause the computer to perform the method 700 and/or anyother functions, operations, or processes described with reference toFIGS. 2-7.

It can be seen from the foregoing description that while currenttechniques for beam search and tracking are based on an active TX STAand an active RX STA iteratively searching first for a sector and thenfor a beam while transmitting signals to one another, the echo-basedbeamforming training techniques described herein utilize a single activeTX STA, without requiring any responsive transmission by the RX STA, todetermine the angle between the TX STA and the RX STA in a single step.This significantly decreases the delay for beamforming training andtracking from milliseconds to microseconds, allowing beamformingtraining to be performed in very dynamic scenarios. Further, theecho-based beamforming training techniques described herein improve theenergy efficiency because the angle determination efficiently utilizesprocessing power to determine the angle in a single iteration orcalculation rather than scanning and transmitting and receiving trainingbased packets.

To provide further context for various aspects of the disclosed subjectmatter, FIG. 8 illustrates a block diagram of an embodiment of userequipment 800 (e.g., a mobile device, communication device, personaldigital assistant, etc.) related to access of a network (e.g., basestation, wireless access point, femtocell access point, and so forth)that can enable and/or exploit features or aspects of the disclosedaspects.

The user equipment or mobile communication device 800 can be utilizedwith one or more aspects of the echo-based beamforming techniquesdescribed herein according to various aspects. The user equipment device800, for example, comprises a digital baseband processor 802 that can becoupled to a data store or memory 803, a front end 804 (e.g., an RFfront end, an acoustic front end, or the other like front end) and aplurality of antenna ports 807 for connecting to a plurality of antennas806 ₁ to 806 _(k) (k being a positive integer). The antennas 706 ₁ to706 _(k) can receive and transmit signals to and from one or morewireless devices such as access points, receive and detect echoes in asignal, access terminals, wireless ports, routers and so forth, whichcan operate within a radio access network or other communication networkgenerated via a network device (not shown).

The user equipment 800 can be a radio frequency (RF) device forcommunicating RF signals, an acoustic device for communicating acousticsignals, or any other signal communication device, such as a computer, apersonal digital assistant, a mobile phone or smart phone, a tablet PC,a modem, a notebook, a router, a switch, a repeater, a PC, networkdevice, base station or a like device that can operate to communicatewith a network or other device according to one or more differentcommunication protocols or standards.

The front end 804 can include a communication platform, which compriseselectronic components and associated circuitry that provide forprocessing, manipulation or shaping of the received or transmittedsignals via one or more receivers or transmitters (e.g. transceivers)808, a mux/demux component 812, and a mod/demod component 814. The frontend 804 is coupled to the digital baseband processor 802 and the set ofantenna ports 807, in which the set of antennas 8061 to 806 k can bepart of the front end. In one aspect, the user equipment device 800 cancomprise a phase locked loop system 810.

The processor 802 can confer functionality, at least in part, tosubstantially any electronic component within the mobile communicationdevice 800, in accordance with aspects of the disclosure. As an example,the processor 800 can be configured to execute, at least in part,executable instructions that estimate the angle between a TX STA and aRX STA. Thus the processor 700 may embody various aspects of the angleestimator circuitry 330 of FIG. 3 and/or 630Rx, 630Tx of FIG. 6.

The processor 802 is functionally and/or communicatively coupled (e.g.,through a memory bus) to memory 803 in order to store or retrieveinformation necessary to operate and confer functionality, at least inpart, to communication platform or front end 804.

The processor 802 can operate to enable the mobile communication device800 to process data (e.g., symbols, bits, or chips) formultiplexing/demultiplexing with the mux/demux component 812, ormodulation/demodulation via the mod/demod component 814, such asimplementing direct and inverse fast Fourier transforms, selection ofmodulation rates, selection of data packet formats, inter-packet times,etc. Memory 803 can store data structures (e.g., metadata), codestructure(s) (e.g., modules, objects, classes, procedures, or the like)or instructions, network or device information such as policies andspecifications, attachment protocols, code sequences for scrambling,spreading and pilot (e.g., reference signal(s)) transmission, frequencyoffsets, cell IDs, and other data for detecting and identifying variouscharacteristics related to RF input signals, a power output or othersignal components during power generation. Memory 803 may include astatic random access memory (SRAM) that stores angle identifiers mappedto RX STAs with which the user equipment 800 is communicating.

Examples herein can include subject matter such as a method, means forperforming acts or blocks of the method, at least one machine-readablemedium including executable instructions that, when performed by amachine (e.g., a processor with memory or the like) cause the machine toperform acts of the method or of an apparatus or system for concurrentcommunication using multiple communication technologies according toembodiments and examples described.

Example 1 is a device that includes a first antenna element. The deviceis adapted for beamforming used in mobile communication and alsoincludes angle estimator circuitry. The angle estimator circuitry isconfigured to cause the first antenna element to transmit anomnidirectional pulse; cause the first antenna element to detect an echoof the transmitted pulse reflected from a second device; estimate anangle between the device and the second device based at least on acharacteristic of the echo; and cause the device to provide the angle tothe second device for use in beamforming between the first device andthe second device.

Example 2 includes the subject matter of example 1, including oromitting optional elements, wherein the omnidirectional pulse comprisesdiscrete coded waveforms.

Example 3 includes the subject matter of example 1, including oromitting optional elements, further including a second antenna elementto be disposed a first distance from the first antenna element. Theangle estimator circuitry is further configured to: cause the secondantenna element to transmit the omnidirectional pulse simultaneouslywith the first antenna element; cause the second antenna element todetect the echo; estimate a second distance between the first antennaelement and the second device; estimate a third distance between thesecond antenna element and the second device; and estimate the anglebased on the first distance, the second distance, and the thirddistance.

Example 4 includes the subject matter of examples 1-3, including oromitting optional elements, wherein the angle estimator circuitry isconfigured to detect the echo based on reflection characteristics in adetected signal that indicate that the signal comprises an echo that isreflected from a communication device.

Example 5 includes the subject matter of examples 1-3, including oromitting optional elements, wherein the angle estimator circuitry isconfigured to cause another angle estimator circuitry associated withthe second device to: cause an antenna element in the second device totransmit a second omnidirectional pulse; cause the antenna element inthe second device to detect a second echo of the second pulse reflectedfrom the device; estimate an angle between the device and the seconddevice based at least on a characteristic of the second echo; and causethe second device to transmit the angle to the device for use inbeamforming between the device and the second device.

Example 6 includes the subject matter of examples 1-3, including oromitting optional elements, wherein the angle estimator circuitry isconfigured to: cause the first antenna element to detect a subsequentecho of the pulse reflected from a third device; estimate an anglebetween the device and the third device based at least on acharacteristic of the subsequent echo; and cause the device to transmitthe angle to the third device for use in beamforming communications withthe third device.

Example 7 is a method, including transmitting an omnidirectional pulseand detecting an echo of the transmitted pulse reflected from a seconddevice with a first antenna element in a device. The method includesestimating an angle between the first device and the second device basedat least on a characteristic of the echo and providing the angle to thesecond device for use in beamforming between the first device and thesecond device.

Example 8 includes the subject matter of example 7, including oromitting optional elements, wherein the omnidirectional pulse comprisesdiscrete coded waveforms transmitted by the first antenna element.

Example 9 includes the subject matter of example 7, including oromitting optional elements, further including transmitting theomnidirectional pulse simultaneously with the first antenna element anddetecting the echo with a second antenna element to be spaced apart fromthe first antenna element by a first distance. The method includesestimating a second distance between the first antenna element and thesecond device; estimating a third distance between the second antennaelement and the second device; and estimating the angle based on thefirst distance, the second distance, and the third distance.

Example 10 includes the subject matter of examples 7-9, including oromitting optional elements, including detecting the echo based onDoppler characteristics in a detected signal that indicate that thedetected signal comprises an echo that is reflected from a communicationdevice.

Example 10 includes the subject matter of examples 7-9, including oromitting optional elements, including receiving an acknowledgementsignal from the second device indicating that the detected echo isreflected from the second device.

Example 12 includes the subject matter of examples 7-9, including oromitting optional elements, further including causing an antenna elementin the second device to transmit a second omnidirectional pulse; causingthe antenna element in the second device to detect a second echo of thesecond pulse reflected from the device; estimating an angle between thedevice and the second device based at least on a characteristic of thesecond echo; and causing the second device to transmit the angle to thedevice for use in beamforming between the device and the second device.

Example 13 includes the subject matter of examples 7-9, including oromitting optional elements, including detecting a subsequent echo of thepulse reflected from a third device; estimating an angle between thedevice and the third device based at least on a characteristic of thesubsequent echo; and transmitting the angle to the third device for usein beamforming communications with the third device.

Example 14 is computer-readable medium having computer-executableinstructions stored thereon that, when executed by a computer, cause thecomputer to: cause a first antenna element to transmit anomnidirectional pulse; cause the first antenna element to detect an echoof the pulse reflected from a second device; estimate an angle betweenthe device and the second device based at least on a characteristic ofthe echo; and cause the device to transmit the angle to the seconddevice for use in beamforming between the first device and the seconddevice.

Example 15 includes the subject matter of example 14, including oromitting optional elements, wherein the omnidirectional pulse comprisesdiscrete coded waveforms transmitted by the first antenna element.

Example 16 includes the subject matter of example 14, including oromitting optional elements, wherein the instructions further compriseinstructions configured to cause the computer to: cause a second antennaelement to transmit the omnidirectional pulse simultaneously with thefirst antenna element; cause the second antenna element to detect theecho; estimate a second distance between the first antenna element andthe second device; estimate a third distance between the second antennaelement and the second device; and estimate the angle based on the firstdistance, the second distance, and the third distance.

Example 17 includes the subject matter of examples 14-16, including oromitting optional elements, wherein the instructions further compriseinstructions configured to cause the computer to detect the echo basedon reflection characteristics in a detected signal that indicate thatthe signal comprises an echo that is reflected from a communicationdevice.

Example 18 includes the subject matter of examples 14-16, including oromitting optional elements, wherein the instructions further compriseinstructions configured to cause the computer to cause another computerassociated with the second device to cause an antenna element in thesecond device to transmit a second omnidirectional pulse; cause theantenna element in the second device to detect a second echo of thesecond pulse reflected from the device; estimate an angle between thedevice and the second device based at least on a characteristic of thesecond echo; and cause the second device to transmit the angle to thedevice for use in beamforming between the device and the second device.

Example 19 includes the subject matter of examples 14-16, including oromitting optional elements, wherein the instructions further compriseinstructions configured to cause the computer to cause the first antennaelement to detect a subsequent echo of the pulse reflected from a thirddevice; estimate an angle between the device and the third device basedat least on a characteristic of the subsequent echo; and cause thedevice to transmit the angle to the third device for use in beamformingcommunications with the third device.

Example 20 includes the subject matter of examples 14-16, including oromitting optional elements, wherein the instructions further compriseinstructions configured to cause the computer to detect the echo basedon Doppler characteristics in a detected signal that indicate that thedetected signal comprises an echo that is reflected from a communicationdevice.

Example 21 is computer-readable medium having computer-executableinstructions stored thereon that, when executed by a computer, cause thecomputer to perform the method of any one of the examples 7-13.

Example 22 is an apparatus, including: means for causing an antennaelement in a first device to transmit an omnidirectional pulse anddetect an echo of the pulse reflected from a second device. Theapparatus also includes means for estimating an angle between the firstdevice and the second device based at least on a characteristic of theecho and means for transmitting the angle to the second device for usein beamforming between the first device and the second device.

Example 23 includes the subject matter of example 22, including oromitting optional elements, including means for causing a second antennaelement that is spaced apart from the first antenna element by a firstdistance to transmit the omnidirectional pulse simultaneously with thefirst antenna element and detect the echo. The apparatus includes meansfor estimating a second distance between the first antenna element andthe second device; means for estimating a third distance between thesecond antenna element and the second device; and means for estimatingthe angle based on the first distance, the second distance, and thethird distance.

It is to be understood that aspects described herein may be implementedby hardware, software, firmware, or any combination thereof. Whenimplemented in software, functions may be stored on or transmitted overas one or more instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a general purpose or specialpurpose computer.

Various illustrative logics, logical blocks, modules, circuitry andcircuits described in connection with aspects disclosed herein may beimplemented or performed with a general purpose processor, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform functionsdescribed herein. A general-purpose processor may be a microprocessor,but, in the alternative, processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, for example, acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration. Additionally, at least oneprocessor may comprise one or more modules operable to perform one ormore of the acts and/or actions described herein.

For a software implementation, techniques described herein may beimplemented with modules (e.g., procedures, functions, and so on) thatperform functions described herein. Software codes may be stored inmemory units and executed by processors. Memory unit may be implementedwithin processor or external to processor, in which case memory unit canbe communicatively coupled to processor through various means as isknown in the art. Further, at least one processor may include one ormore modules operable to perform functions described herein.

Further, the acts and/or actions of a method or algorithm described inconnection with aspects disclosed herein may be embodied directly inhardware, in a software module executed by a processor, or a combinationthereof. A software module may reside in RAM memory, flash memory, ROMmemory, EPROM memory, EEPROM memory, registers, a hard disk, a removabledisk, a CD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium may be coupled to processor, such thatprocessor can read information from, and write information to, storagemedium. In the alternative, storage medium may be integral to processor.Further, in some aspects, processor and storage medium may reside in anASIC. Additionally, ASIC may reside in a user terminal. In thealternative, processor and storage medium may reside as discretecomponents in a user terminal. Additionally, in some aspects, the actsand/or actions of a method or algorithm may reside as one or anycombination or set of codes and/or instructions on a machine-readablemedium and/or computer readable medium, which may be incorporated into acomputer program product.

In this regard, while the disclosed subject matter has been described inconnection with various embodiments and corresponding Figures, whereapplicable, it is to be understood that other similar embodiments can beused or modifications and additions can be made to the describedembodiments for performing the same, similar, alternative, or substitutefunction of the disclosed subject matter without deviating therefrom.Therefore, the disclosed subject matter should not be limited to anysingle embodiment described herein, but rather should be construed inbreadth and scope in accordance with the appended claims below.

What is claimed is:
 1. A device comprising: a first antenna element;angle estimator circuitry configured to: cause the first antenna elementto transmit an omnidirectional pulse; cause the first antenna element todetect an echo of the transmitted pulse reflected from a second device;estimate an angle between the device and the second device based atleast on a characteristic of the echo; and cause the device to providethe angle to the second device.
 2. The device of claim 1, wherein theomnidirectional pulse comprises discrete coded waveforms.
 3. The deviceof claim 1, further comprising: a second antenna element to be disposeda first distance from the first antenna element; wherein the angleestimator circuitry is further configured to: cause the second antennaelement to transmit the omnidirectional pulse simultaneously with thefirst antenna element; cause the second antenna element to detect theecho; estimate a second distance between the first antenna element andthe second device; estimate a third distance between the second antennaelement and the second device; and estimate the angle based on the firstdistance, the second distance, and the third distance.
 4. The device ofclaim 1, wherein the angle estimator circuitry is configured to detectthe echo based on reflection characteristics in a detected signal thatindicate that the signal comprises an echo that is reflected from acommunication device.
 5. The device of claim 1, wherein the angleestimator circuitry is configured to cause another angle estimatorcircuitry associated with the second device to: cause an antenna elementin the second device to transmit a second omnidirectional pulse; causethe antenna element in the second device to detect a second echo of thesecond pulse reflected from the device; estimate an angle between thedevice and the second device based at least on a characteristic of thesecond echo; and cause the second device to transmit the angle to thedevice.
 6. The device of claim 1, wherein the angle estimator circuitryis configured to: cause the first antenna element to detect a subsequentecho of the pulse reflected from a third device; estimate an anglebetween the device and the third device based at least on acharacteristic of the subsequent echo; and cause the device to transmitthe angle to the third device.
 7. A method, comprising: causing anantenna element in a first device to transmit an omnidirectional pulse;and detecting an echo of the transmitted pulse reflected from a seconddevice; estimating an angle between the first device and the seconddevice based at least on a characteristic of the echo; and providing theangle to the second device.
 8. The method of claim 7, wherein theomnidirectional pulse comprises discrete coded waveforms transmitted bythe first antenna element.
 9. The method of claim 7, further comprising:with a second antenna element to be spaced apart from the first antennaelement by a first distance: transmitting the omnidirectional pulsesimultaneously with the first antenna element; and detecting the echo;estimating a second distance between the first antenna element and thesecond device; estimating a third distance between the second antennaelement and the second device; and estimating the angle based on thefirst distance, the second distance, and the third distance.
 10. Themethod of claim 7, comprising detecting the echo based on Dopplercharacteristics in a detected signal that indicate that the detectedsignal comprises an echo that is reflected from a communication device.11. The method of claim 7, comprising receiving an acknowledgementsignal from the second device indicating that the detected echo isreflected from the second device.
 12. The method of claim 7, furthercomprising: causing an antenna element in the second device to transmita second omnidirectional pulse; causing the antenna element in thesecond device to detect a second echo of the second pulse reflected fromthe device; estimating an angle between the device and the second devicebased at least on a characteristic of the second echo; and causing thesecond device to transmit the angle to the device.
 13. The method ofclaim 7, further comprising: detecting a subsequent echo of the pulsereflected from a third device; estimating an angle between the deviceand the third device based at least on a characteristic of thesubsequent echo; and transmitting the angle to the third device. 14.Non-transitory computer-readable medium having computer-executableinstructions stored thereon that, when executed by a computer, cause thecomputer to: cause an antenna element in a first device to transmit anomnidirectional pulse; and detect an echo of the transmitted pulsereflected from a second device; estimate an angle between the firstdevice and the second device based at least on a characteristic of theecho; and provide the angle to the second device.
 15. The non-transitorycomputer-readable medium of claim 14, wherein the omnidirectional pulsecomprises discrete coded waveforms.
 16. The non-transitorycomputer-readable medium of claim 14, wherein the instructions furthercomprise instructions configured to cause the computer to: cause asecond antenna element to transmit the omnidirectional pulsesimultaneously with the first antenna element, wherein the secondantenna element is spaced apart from the first antenna element by afirst distance; cause the second antenna element to detect the echo;estimate a second distance between the first antenna element and thesecond device; estimate a third distance between the second antennaelement and the second device; and estimate the angle based on the firstdistance, the second distance, and the third distance.
 17. Thenon-transitory computer-readable medium of claim 14, wherein theinstructions further comprise instructions configured to cause thecomputer to detect the echo based on reflection characteristics in adetected signal that indicate that the signal comprises an echo that isreflected from a communication device.
 18. The non-transitorycomputer-readable medium of claim 14, wherein the instructions furthercomprise instructions configured to cause the computer to cause anothercomputer associated with the second device to: cause an antenna elementin the second device to transmit a second omnidirectional pulse; causethe antenna element in the second device to detect a second echo of thesecond pulse reflected from the device; estimate an angle between thedevice and the second device based at least on a characteristic of thesecond echo; and cause the second device to transmit the angle to thedevice.
 19. The non-transitory computer-readable medium of claim 14,wherein the instructions further comprise instructions configured tocause the computer to: cause the first antenna element to detect asubsequent echo of the pulse reflected from a third device; estimate anangle between the device and the third device based at least on acharacteristic of the subsequent echo; and cause the device to transmitthe angle to the third device.
 20. The non-transitory computer-readablemedium of claim 14, wherein the instructions further compriseinstructions configured to cause the computer to detect the echo basedon Doppler characteristics in a detected signal that indicate that thedetected signal comprises an echo that is reflected from a communicationdevice.